The use of hollow polycarbonate containers such as bottles, jars and packages for storing food, beverages, and other perishable items has been finding increased use. Polycarbonate containers offer several advantages over comparable glass containers. These advantages include lighter weight, and greater impact strength and resistance to breakage. These advantages are achieved without any sacrifice in the optical clarity and transparency of the polycarbonate containers as compared with glass containers.
However, polycarbonate containers suffer from the disadvantage of being relatively more permeable to gas transport than glass containers. Thus, for example, glass containers are better for storing carbonated beverages as they are better at keeping in the CO.sub.2 than polycarbonate containers. Likewise, glass containers are more effective than polycarbonate containers in keeping out oxygen from juices and other perishable foods, thereby preventing these perishable items from spoilage for longer periods of time than polycarbonate containers.
In order to remedy this relatively high gas permeability of polycarbonate containers U.S. Pat. No. 4,327,137 discloses utilizing a two layer hollow container comprised of a polycarbonate inner layer and a polyester outer layer. The polyester layer functions as a gas-barrier layer. While such two layer containers are effective in reducing the gas transport between the interior of the container and the outside environment, they nevertheless suffer from several disadvantages. Firstly, the exposed polyester layer is subject to hydrolytic degradation at conditions of high humidity and high temperature. These conditions are usually present during washing of the containers. The polyester is also subject to shrinkage caused by crystalline change at high temperatures. Secondly, the polyester is quite sensitive to hot caustic solutions. Since most reusable bottles or containers are washed with a hot cleaning solution containing caustic, these two layer containers are unsuitable for use as reusable containers.
It is, therefore, an object of the instant invention to provide polycarbonate containers which exhibit improved gas-barrier properties and improved resistance to hydrolysis and attack by caustic agents.